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Influence of Lubricants on the Thermal Behaviour of Rotary Shaft Seals
Many applications require seals that retain lubricants (e.g. oil) or other fluids within machines and prevent the entry of dirt into these machines. In applications with rotating shafts, mostly elastomeric rotary shaft lip-type seals are used. The rotary shaft seal, the shaft surface and the fluid, which has to be sealed, form a tribological system, that is significantly affected by its periphery and the operating conditions.
During operation, energy is dissipated in the contact area between the sealing edge and the shaft surface due to friction. This means, kinetic energy is converted to frictional heat. The temperature in the contact area is higher the more frictional heat is generated and the poorer this heat is transferred away from the contact area. High contact temperatures are very harmful to the sealing system and reduce its lifetime. Therefore, it is very important to know the temperature in the contact area as accurately as possible and to keep it within acceptable limits.
The contact temperature of a sealing system can be found either by simulating the fluid flow and heat transfer in the sealing system and its periphery or by measurements during test runs. The measurement of the contact temperature is the topic of this paper. In this work, the influence of different lubricants and different shaft coatings is analysed. Therefore, the friction torque is measured during test runs at a test rig. Additionally, the temperature at the air side of the sealing edge is measured using an infrared thermal imager.
The test runs are performed with 15 different mineral and synthetic (PAO, PG, ester) oils. The measurement results are used to expand the “ExACT” algorithm, that is used in the online tool “InsECT” for estimating the contact temperature of rotary shaft seals.